1. Field of the Invention
This application pertains to the art of automatic gas and oil wells and, more particularly, to electronically controlled gas and oil wells having a sales conduit or tubing string between a subterranean fluid producing formation and a surface reservoir for storing the fluids produced through the conduit or tubing string.
The invention is particularly applicable to a system employing a plunger or "rabbit" device having a radially expansible portion and an electronic sequencer for controlling the overall gas and oil well system and will be described with particular reference thereto, although it will be appreciated that the invention has broader applications such as swabbing uses and production from wells having a horizontal tubing string made to lie within a narrow producing formation stratus.
2. Description of Prior Art
Production well systems have heretofore comprised a plunger having an elongated and generally cylindrical body portion received into a tubing string surrounded by a casing. The body portion of the plunger is typically provided with a seal for engagement with the inner wall of the tubing string to restrict the flow of fluids around and past the plunger body. Complicated internal valves have been provided within the plunger body to both restrict the flow of fluids through the plunger body itself and to help reduce the free-fall speed of the plunger during its descent from the well head at the surface toward the formation below ground. It is important that the descent speed be held in check due to the deleterious forces generated between the outer seal and the inner conduit wall. U.S. Pat. No. 4,070,134 to Gramling shows such a plunger.
More recently, swabbing systems have been developed using plungers with a radially expansible portion for sealing engagement with a casing responsive to pressure below the plunger and communicated through plunger body orifices beneath the expansible portion. Further, internal valves have been implemented by way of shift rods received axially into the plunger body. U S. Pat. No. 4,813,485 to Coyle shows such apparatus.
Present methods for controlling gas and oil wells using plungers of the type described above involve cyclic operation of the device responsive to pressure differentials above and below the plunger by means of internal pressure sensing apparatus. Plunger catch mechanisms have also been attempted to mechanically catch the plunger at an upper extreme of travel. The plunger is released either by manual means or by an enhanced catch mechanism responsive to pressure differentials within the tubing string and atmosphere. As such, truly automated operation is not possible. It has, therefore, been deemed desirable to provide an economical and efficient solution that meets the various operational conditions encountered at various installations.